Screening of solid particulate materials to form separate fractions of differently sized particulates is undertaken for many purposes. One such purpose is to separate desired from undesired particulates from a solid particulate material containing each if such may be accomplished based on a size differential between the desired and the undesired particulates. An example of such is the removal of aluminium oxide powder, also called alumina powder, from a solid particulate material so the desired powder may be fed to, for example, an aluminium production electrolytic cell utilized in the production of aluminium as disclosed in US 2009/0159434. Screening of solid particulate material is typically done by passing the particulate material through a perforated screening plate. In this way, desired particulates of the desired size may be separated from the solid particulate material.
JP-8299909 discloses a fluidized bed chamber having a vertical plate, which operates as a screening plate to separate particles into a fine particle fraction and a coarse particle fraction. Particles of both sizes are introduced into the fluidized bed chamber and pass through the screening plate into a take off chamber having separate take off ports for each fine particles and coarse particles. However, the screening device disclosed in JP-8299909 is considered inefficient and may provide inaccurate screening.